CVE-2026-43278: dm: clear cloned request bio pointer when last clone bio completes

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-06 · updated 2026-10-19
Weakness: CWE-415

Description

In the Linux kernel, the following vulnerability has been resolved: dm: clear cloned request bio pointer when last clone bio completes Stale rq->bio values have been observed to cause double-initialization of cloned bios in request-based device-mapper targets, leading to use-after-free and double-free scenarios. One such case occurs when using dm-multipath on top of a PCIe NVMe namespace, where cloned request bios are freed during blk_complete_request(), but rq->bio is left intact. Subsequent clone teardown then attempts to free the same bios again via blk_rq_unprep_clone(). The resulting double-free path looks like: nvme_pci_complete_batch() nvme_complete_batch() blk_mq_end_request_batch() blk_complete_request() // called on a DM clone request bio_endio() // first free of all clone bios ... rq->end_io() // end_clone_request() dm_complete_request(tio->orig) dm_softirq_done() dm_done() dm_end_request() blk_rq_unprep_clone() // second free of clone bios Fix this by clearing the clone request's bio pointer when the last cloned bio completes, ensuring that later teardown paths do not attempt to free already-released bios.

Affected products

Linux kernel: from 6.1 before 6.1.165; from 6.2 before 6.6.128; from 6.7 before 6.12.75; from 6.13 before 6.18.16; from 6.19 before 6.19.6 — fixed in 6.1.165, 6.12.75, 6.18.16, 6.19.6, 6.6.128

How to fix

Upgrade to a fixed version: Linux kernel 6.1.165, 6.12.75, 6.18.16, 6.19.6. Check the vendor advisory for mitigations.

References

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